It is a problem in the field of cellular communication networks to enable a mobile subscriber to receive SMS text messages and Voice-Mail/Message Waiting Indications when they roam outside the coverage area of the cell in which they are presently registered and more particularly when they encounter a border condition between Mobile Switching Centers.
Mobile service providers seek to increase the maximum number of Busy Hour Call Attempts (BHCA) in order to serve the ever-increasing number of mobile subscribers. One of the major roadblocks to increasing the number of mobile subscribers served by a Mobile Switching Center is the availability of sufficient paging channel bandwidth between the Mobile Switching Center and the mobile subscriber stations. The paging channel is a channel used by the cell to send pages, which indicate incoming calls, to the mobile subscriber station.
However, SMS traffic also uses the paging channel to deliver messages to the mobile subscriber stations. This service has doubled in the past few years and continues to increase significantly each year. This growth is due to both the rapid growth in SMS messaging resulting from the popularity of text messaging between subscribers and the increase in service provider services, such as the use of SMS to provide Voice Mail/Message Waiting Indications. These services collectively consume a significant amount of the paging channel bandwidth, which is a critical network resource, and the paging channel is on the threshold of full utilization, thereby impeding the ability of the Mobile Switching Centers to serve additional call attempts from mobile subscriber stations.
This problem is most commonly encountered in the case of a border service area, which is the location where the service area of a first Mobile Switching Center overlaps the service area of a second Mobile Switching Center. This situation occurs because the cell site radio frequency signals transmitted by the various base station subsystems served by the Mobile Switching Centers are not precisely bounded; and to provide continuity of service to the mobile subscribers, the radio frequency signals from one base station subsystem must overlap with the radio frequency signals from an adjacent base station subsystem. Therefore, the mobile subscriber stations are designed to select the base station subsystem originating the strongest signal to ensure reliable communications as the mobile subscriber roams among multiple cell sites.
In this environment, when the mobile subscriber's movements cause the mobile subscriber station to switch among cell sites on a frequent basis (termed “border condition” herein), the mobile subscriber is not provided with accurate message waiting indications and cannot reliably receive the SMS text messages. This is due to the fact that, when the subscriber roams among multiple cell sites served by different Mobile Switching Centers, the mobile subscriber station performs an Autonomous Registration with the new Mobile Switching Center each time the mobile subscriber traverses the border between the service areas of adjacent Mobile Switching Centers (MSC). The Serving Mobile Switching Center registers the mobile subscriber station at its Home Location Register, which then returns the subscriber profile data indicating the features and call data specific for this mobile subscriber station. The mobile subscriber is unaware of this process, and it represents a cellular communication network administrative process that is required to accurately record the present location of the mobile subscriber station in the cellular communication network for call routing purposes, and to provide the mobile subscriber with the set of features for which they are enrolled.
This problem is most serious in a highly congested cellular communication network where there are many border cells. In this environment, when the call handling capacity of a Base Station Subsystem is reached, an additional Base Station Subsystem is added to the Mobile Switching Center to provide the necessary call handling capacity. However, when the call handling capacity of a Mobile Switching Center is reached, the coverage area of the Mobile Switching Center is reduced and a new Mobile Switching Center is installed, thereby creating more border cells. With the increased subscriber population and longer holding times on calls due to new media-based applications, this problem is becoming more prevalent.
This process can continue seriatim as the subscriber roams through various call coverage areas, since each Mobile Switching Center is unaware of the acknowledgement transmitted by the mobile subscriber station to the original Mobile Switching Center and any other previously contacted Mobile Switching Centers. In a highly congested cellular communication network or a cellular communication network with many border cells, the number of paging channel message transmissions becomes excessive and serves to congest the paging channel with unnecessary messages. Ultimately, the paging channel congestion can result in the loss of new call originations and call deliveries.